Camera Lens Protection

I'm on the fence with this one.  It checks the boxes for battery life (enough to do a century).  All in all this device seems very convenient for having 3 things in 1.  I'm trying to weigh if it makes sense for my situation.

--Has anyone found a good way of protection a camera lens on this type of device on the back of a seat post?  I ride a LOT of gravel in national forests and fully expect sand and stones to hit this thing.  My varia 510 tends to be covered in dirt and grit after 1/2 of my rides.  I'm not sure that helicopter tape would work for that? (  Does anyone know if it protects for impact?  It would be fine for scratches).  Then again I've not confirmed if helicopter tape would harm the image quality. 

*EDIT* I've gone ahead and ordered mine.  However if anybody comes up with ideas for a camera lens protector for rocks, I'd love to hear them.